The present invention relates to a hot fill apparatus and process for use in the manufacture of hollow blow molded containers constructed from a thermoplastic, such as a thermoplastic polyester or a biaxially oriented polyethylene terephthalate resin. Hollow blow molded thermoplastics are commonly used as containers for food and beverages. Such containers, particularly containers constructed of a biaxially oriented polyethylene terephthalate resin (xe2x80x9cPETxe2x80x9d), must be periodically tested during manufacture for structural resiliency under hot fill and cold fill applications. For instance, in manufacturing operations producing between 5,000 and 50,000 containers per hour, batches of the containers are regularly tested, in many cases on an hourly basis, to ensure continued quality of manufacture. These requirements are met by a hot fill apparatus which fills the container with hot water, commonly maintained at a temperature close to boiling and then quick cools the container. The hot fill and quick cool application of water to a container provides a quality check of the resiliency of the container shape against expansion, contraction and undesirable deformation.
Flow through hot fill machines are designed to maintain a specified pressure and flow rate of water through the apparatus regardless of whether the apparatus is in use. Maintenance of flow rate and pressure are necessary to maintain strict regulation of water temperature within the hot fill apparatus. Some prior art hot fill machines will use at least one xe2x80x9cinstant heatxe2x80x9d water heater and commonly use up to three such water heaters linked in combination to maintain strict temperature control of the water. Such water heaters demand a constant flow rate and a constant pressure of water passing through the heaters to prevent damage to the heaters. Commonly, the pressure is maintained at or above a required minimum of 20 psi and the flow rates are maintained at or above a required minimum of 1.5 gallons per minute with an optimum flow rate being 3 gallons per minute. Thus, some prior art flow-through hot fill machines have a water flow control system which provides a desired input volume into the heating loop and maintains a desired output volume from the heating loop. When the machine is not in use, the water output from the heating loop commonly enters a bypass flow to a drain.
Hot fill machines commonly have a number of faults which make them unreliable and many times undesirable.
Hot fill machines commonly work with conditioned water, water obtained from municipal water sources, and well water. Most water, even softened water, contains undesirable amounts of chemicals, minerals and other contaminants such that scale and chemical or mineral deposits will be formed, over time, on the heaters. An accumulation of scale or deposits on the heaters cause the heater mechanisms to become inefficient, resulting in premature failure and overloading of the heaters, thereby shutting down the machine and forcing costly repairs. Thus, it is desirable to provide a hot fill machine and process that can treat the input water prior to heating to remove undesirable chemicals, minerals and other contaminants.
Many common prior art hot fill machines use a spring activated valve or nozzle which is pressed upon the thermoplastic container mouth to open the valve and cause the hot fill water to flow into the container. Such spring activated valves sometimes put too much pressure on the container and have been known to deform or crush the container. A hot fill machine having a redesigned valve member is desired.
The present invention provides solutions to the above problems in the following manner. Water intended to flow to the heaters is first received from the water source and treated by a reverse osmosis filtration system. The reverse osmosis filtration system serves to trap and eliminate most all minerals and chemicals which are known to deposit upon and contaminate the heaters, thereby eliminating many known causes of heater inefficiency and premature failure. The reverse osmosis system as incorporated in this hot fill machine ideally uses a carbon canister having 2 parts per million chlorine removal capability with a backflush provision. The flow rate into the reverse osmosis system is designed to provide the desirable input flow into the heaters, thereby creating the desirable output flow from the heaters. The reverse osmosis system by nature of its operation creates an output flow rate which is less than the input flow rate, commonly by a ratio of three to one. For instance, one embodiment of the invention will input water at 6 gallons per minute into the reverse osmosis system to receive an output of clean uncontaminated water at 2 gallons per minute which flows to the heater mechanisms. The 4 gallons per minute flow differential is either recirculated back to the inlet side of the water pump or, if the water is heavily contaminated, is dumped to the drain. The reverse osmosis system, as incorporated into this invention, is designed with an automatic backwash for the carbon tanks which is operational when it is sensed within the hot fill apparatus that the system is in idle and not being used for hot fill applications.
The fill mechanism of the hot fill apparatus of this invention is normally provided with, for alternative usage, an on/off spigot and an automatic fill head. The spigot is used for any purpose and is not controlled by the height, volume and top load force variables which are used to control the fill head. The automatic fill head includes a rodless air cylinder with an adjustable slide through which an operator can dial in the bottle height and top load which is desired to simulate the load that a container will experience when filled with end product. Commonly, the top load is greater than 3 pounds, but less than 14 pounds. After the operator has established the bottle size and top load, the fill head is automatically activated to hot fill the container. Sensors act to sense the fill level and discontinue the fill and return the fill head to its original start position. Alternatively, controls are provided through which an operator can adjust the amount of fluid flowing into a container, thereby causing the fill head to automatically shut off. An override switch is also provided which can deactivate or activate the fill nozzle solenoid at any point in the cycle.
The hot fill machine is designed to have continuous flow and is provided with a normally open solenoid valve that directs flow to the drain and automatically closes when either the spigot or the fill head is activated. The spigot and fill head cannot be activated at the same time, thereby assisting and maintaining the controlled flow and temperature required for the proper operation of the hot fill apparatus.
These inventive aspects of the hot fill apparatus and process are achieved by the apparatus described and disclosed in the following drawings.